A check valve for fluid bladders in combination with a pumping chamber and inflatable bladder similar to the present invention is disclosed in my U.S. Pat. No. 5,144,708 ('708 Patent). The pumping chamber and inflatable bladder have two sheets of heat-sealable material sealed about the periphery thereof. The check valve comprises two superposed sheets or films of heat-sealable material sealed together along their sides to form a channel therebetween to permit fluid flow therethrough. The check valve is heat-sealed between the pumping chamber and the inflatable bladder at one end thereof to provide one-way fluid flow from the pumping chamber to the bladder. The two sheets which form the check valve are coated by a barrier material at the location in which the valve is to be heat-sealed between the pumping chamber and bladder to prevent the check valve from being sealed "closed."
As disclosed in the '708 Patent, the check valve is of generally rectangular form. The seal that secures the check valve between the pumping chamber and bladder is chevron shape with its apex pointed towards the pumping chamber or inlet end of the valve. The chevron shape seal facilitates the opening of the check valve during the pumping action. The pumping action forces the fluid against the apex of the chevron seal, causing the seal to separate or peal back to thereby "open" the check valve to permit fluid to flow therethrough.
It has been found though that the rectangular check valve disclosed in the '708 Patent exhibits sporadic difficulty in pumping when the sheets of material used to form the pumping chamber and inflatable bladder, such as a combination of film and fabric, are relatively stiff. The difficulty in pumping arises because portions of the inlet end of the valve, which are not sealed to the outer sheets, remain fused together during the pumping action. The stiff material reduces the degree of expansion across the V-shape seal such that the unsealed inlet edge does not fully "open" thereby reducing the fluid flow which makes the pumping action difficult.
In addition, it has been found that the initial flow of fluid through the check valve for the first time may, on occasion, be blocked because of incidental sticking together of the layers adjacent the outlet end of the valve.